Recuperative soaking pit furnace



W. A. MORTON ET AL RECUPERATIVE SOAKNG PIT FURNACE 12 sheets-shed 1 IOriginal Filed Feb. 14,` 1934 bld-1 ,ffii/151%, r

RNEY

w. A. MoRToN ET AL 2,079,560

RECUPERTIVE SOAKNG PIT FURNACE gnal Filedv Feb. 14, 1934 l2She'ets-Sheet 2 May 4, 1937.

WH my y R NNN Troma-Y May 4, 193 7.

w.' A; MoRToNjL-:r AL

RECUPERATIVE SOAKING PI`T FURNACE 12 Sheets-Sheet 4 Original Filed Feb.14, 1934 WYENTORS' sry' BYV 'Www/EJ' WAM ATTORNEY May 4, 1937.

W. A. MORTON ET AL RECUPERATIVE SOAKING PIT FURNACE Original Filed Feb.14, 1954` 12 sheets-sheet 5 i?? zo.

INVENTORS ma. M

A TTORNEY w.` A. MoRToN Er Al. 2,079,560

RECUPERATIVE SOAKNG PIT FURACE original Filed Feb. 14, 1954 12sheets-sheet e IN VENT ORS A TTORNEY May 4, 1937.

May 4, 1937. w. A. MoRToN ET AL 2079560 RECUPERATIVE SOAKNG PIT FURNAGEI original Filed Feb. 14, 1934 12 sheets-sheet 7 ATTORNEY 12Sheets-sheet 9 Tm J W. A. MORTON ET AL LREGUPERATIVE soAKING PIT Mmmm:`

Original Filed Feb.. 14, 1934 I. -l a..

May 4, 1937.

INVENTORS i, ma... a, ama.. BY #ww-:44;: s

.d ATT RNEY MY 4, 1937. w. A; MoRToN Er AL 2,079,550

REGUPERATIVE soAKING PIT FlmucE Original Filed Feb. 14, '1934 12Sheets-Sheet 10 BY'WASM May 4, 1937. w. A. MoBToN ErAp.

RECUPERATIVE:V `stumme ,PIT FURNACE original Filed Feb. k14, 1954 12-sheets-sheet 12 SQN UU DD DDD DD. UD

d WN

Q .mrc

Uhm,

INVENToRs f ATTORNEY l Patented `May 4, 1937 UNITED STATES PATENTNoI-rlclaz' i 2,079,560

nacuraiwnvg soAxING rrr FunNAvcu wuuamn. Morton and Howard F. spencer,Pittsburgh, Pa., assignors to Amco, Incorporated, Pittsburgh, Pa., acorporation of Pennsylvania Application February 14, 1934, Serial No.711,166

' Renewed July 23, 1936 26 claims. (c1. zes-15) This invention relatesto pit furnaces of the recuperative type for the reheating of ingots torolling temperatures after they are stripped from their molds, and it isamong the objects thereof to provide a pit Vfurnace in which the ingotsare arranged and the combustion gases introduced Another object of theinvention is the provision .of a pit furnace in which the ingots arearranged to form a combustion chamber between the ingot walls.

Another object of the invention is the provision of a pit furnace inwhich the combustion 'gases are introduced vertically into thecombustion chamber.

A further object of the invention is the pro-l vision of'a pit furnacein which the combustion gases are introduced into and the products ofcombustion withdrawn from the bottom of the furnace.

vStill a further object of the invention is the construction of afurnace in which the combustible gases are introduced vertically intothe center of a plurality of spaced ingots and in'which the products ofcombustion are removed through spaced outlets at substantially thebottom of the furnace.

Still a further object of the invention is the construction of a pitfurnacein which a mixing chamber for air and gas is provided below thehearth of the pit and in Vwhich the combustible mixture isdirected-vertically through' a rlng port at substantially the center ofthe furnace.

These and other objects of the invention will become more :apparent froma consideration of the accompanying drawings-constituting a part hereofin which like reference characters desig taken along the Figure 4 avertical section takenon thevline Figure 5 a vertical section taken onthe line,

V-V, Figures 1 and 3;

Figure 6 a vertical section which is an extension Figure 7' a verticalsection taken on the line VII-V11, Figure 3;

Figure 8 a vertical section forming an extension of the Asection shownin Figure 7;

Figure 9 a vertical section taken on the line 5 IX-IX, Figure 3; i

Figure 10 a vertical section forming an extension of Figure 9;

Figure 11 a vertical section taken on the line I I-.IL Figure 3: Y 1oFigure .12 a top plan view of the stack endV of the furnace showing thevalve arrangement `of the air and gas passages;

Figures 13 and 14 vertical sections taken on the lines XIII-XIII andXIV-#HV respectively 15 of Figure 12;

Figure 15 a reduced top plan view of a portion `of a pit furnace asshown in Figure 1, illustrating an oval shaped rlng port; o

Figure 16 a vertical section showing a modi m iication of therecuperator structure of Figure 3; Figure 17 a vertical half section ofa modified recuperator structure taken on the line XVII, Figure 18; and

Figure 18 a horizontal cross-section of -Figure 25 17 taken on the lineXVIII, Figure 3.`

" The structure will be first briefly explained in connection withFigures 1, 2 and 3 of the drawings. As shown in Figure 3, the referencenumeral I generally designates a pit furnace in 3@ which a. pluralityof, ingots.2 are seated on a hearth 3 in spaced relation as is moreclearlyv shown in Figure 1, the ingots being disposed around a ring port4 projecting centrally of the pit furnace I, the wall i of the port Iextending above 4a. bed of coke breeze designated by the numeral 6.Grooves I are provided in the hearth 3 for drainingl any molten metalthat may accumulate on the hearth surface into a pit 8, an outlet 8abeing provided for removing the slag 4o and clearing the pit. A cleaningdoor 9 is also provided for removing the accumulated material from thebottom of the firing port. The pit is constructed of ,suitablerefractory walls III and may be of rectangular form as shown in Figure 1or may be otherwise shaped such as round or oval if desired as shown inFigure 15. Agcover II of refractory material ls adapted to close the4pit I after the ingots are charged therein, the cover being supported onwheeled axles I 2 that 50 operate on rails I3 provided above the pitfurnace, the movements of the cover II being effected by a drivemechanism operated by a motor I5 shown in Figure 4 of the drawings.Opposite walls of the pit furnace are provided 5l with exit passages I6to draw off Waste gases to recuperator structures generally designatedby numerals I1, the passages I6 being controlled by dampers I8 toregulate the withdrawal of the products of combustion from oppositewalls of the furnace. The recuperators I1 are of the usual tileconstruction, the tile I9 forming vertical waste gas passages 20 andtransverse air passages leading to inlets/2|, the air entering at thebottom of the tile structure and passing transversely across the tile inan upward direction absorbing the waste heat of the products ofcombustion passing through the tile until in its preheated condition itpasses into ports 22` leading to a combustion chamber 23 beneath thefiring port 4. Combustible gas such as producer gas is supplied throughpassages 24 and enter the combustion chamber 23 through ports 25, thecombustible gas co-minging with the preheated air of ports 22 andbecoming thoroughly mixed in the mixing chamber 23, thence passingvertically upward through the firing port 4 into the pit furnace.

Burner ports 26 may be provided in the mixing chamber 23 to use low B.t. u. gases such as blast furnace gases which, with the high preheat ofthe recuperator, can be utilized forl emcient heating at low cost.

Clean-out openings 21 are provided in the recuperator wall to clean outthe waste gas passages I6 leading to the recuperators, and clean-outopenings 28 -are provided to clean out the slag or other foreignmaterials accumulated frompits 29 at the bottom of the recuperator tilethrough which the waste gases pass to fiues 30 leading to the gallery3l, Figure 2, communicating with the stack 32.

The structure described in connection with Figure 3 is shown inmultiples in Figures 1 and 2 in which three pit furnaces and theirrecuperator structures are shown.

Figure 5 is a vertical section taken transversely of the section ofFigure 3 along the line V--V of Figure 3 which is the center line andthis view clearly yillustrates the gas exit passages I6 and the burnerports 26 for the blast furnace gases.

It also illustrates the frame structure on which the pit furnaces aresupported.

Figure 11 is a vertical section taken on the line XI--XL Fig-ure 3,which is through the center of the recuperators, this view showing thegas exits I6, their controlling dampers I8 and the preheated air ports22, and generally illustrates the nature of the recuperator structure.

Figure 9 is a vertical section taken through the passages. of the lwastegases after they leave the recuperators I1, this view and its extension,Figure l0, being taken on the line IX-IX Figure 3. 'Ihese views show thepassages 23 at the bottom of the recuperator communicating with passages3I'I which in Figure 12 are shown leading to passages 34 having a commonconnection with the gallery 3| leading to the exhaust stack 32. Figure 9also shows the preheated air ports 22, the waste gas exits I6, and acooling flue 35 through which a cooling blast is conducted by passages36.

Figure' is a vertical section through the-combustible gas passages 24taken along the line VII-VII of Figure 3, there being a passage and port25 for each pit furnace, the extension of Figure '7 being shown inFigure 8 wherein the gas passages 24 communicate with a common gas fnain31 from which the gas is distributed to pas- ?sages 24 by means ofcontrol valves 38 shown in '.-Y-.z-.f'section in Figure 6 of thedrawings, The valve chambers 33 are provided with removable covers 40through which valve stems 4I project, valve stems 4I being operable bycables 42 passing over sheave wheels 43 and 44 as shown in Figure 13,this view also showing dampers 46 for controlling a flow of waste gasfrom the passages 3l to the main, passages 46 leading to the stack 32,the arrangement of gas valves 33 and dampers 45 of Figure 13 being shownin a top plan view of Figlure 12 which also shows the combustible gaspassages 41 for the producer gas, there being one passage 41 on eachside of the stack 32 for each set of recuperators on the sides of thepit furnaces. Passages 41 are provided with air inlet passages 43provided with doors 49 for purpose to be hereinafter explained.

Figure 15 shows a modification of the shape of the burner port in thehearth, this curved form being preferred to give the port wallsadditional strength to maintain a more uniform area and resist loadingof the hearth and expansion and contraction.

The structure shown in Figure 16 is identical with that disclosed inFigure 3 with the exception that the structure of Figure 3 is cutthrough the center line, and the half sections are disposed back to backwith their recuperator structures forming adjacent members so that whatwould be a single pit furnace in Figure 3 of the drawings for example ismade two separate pit furnaces separably operable through theirrecuperator and burner port structures.

'I'he structure of Figure 16 would be operable in the same manner asthat of Figure 3 in that the combustible gases are directed verticallyupward from the bottom orhearth of the pit and the products ofcombustion are withdrawn horizontally adjacent the bottom of the pit tothe waste gas iiues I6.

The operation of the above described pit furnace is brieiiyas follows: y

Groups of pit furnaces such as shown in Figlires 1 and 2 illustratingthree pit furnaces may be operated individually or in separatelycontrolled multiples of any number. The ingots after they are strippedare charged into the respective pit furnaces in such manner that theyare disposed around the firing ports 4 in the bottom of the pits, theports being shown as of rectangular construction in Figure 1, althoughthey may be of any desired shape or such as shown in Figure l5.

When the pits are charged, air and gas are conducted through theirrespective ports `22 and 26 into the mixing chamber 23 where thecombustible mixture is accumulated and the resultant flame passesthrough-the firing port 4 vertically upward into the pit furnace andinto the combustion chamber between the walls of the spaced ingots.

The gases then'pass vertically upward with the initial flamesubstantially out of contact with the ingot walls, the fiame andproducts of combustion being deflected by the cover II, thev gases thenare diffused and the denser products passages 30, Figure 9, passages 34,Figure 10,

to the waste gas passage 48 tothe stack 32, the flow of the waste gasesbeing controlled by dampers I8, Figure 3, and dampers 45,

Figure 13. Dampers Il regulate the flow of waste gases from therespective sides of the pit furnaces whereby .the temperature along theside walls of the ingots may be regulated, and the main dampers lcontrol the withdrawal of gases from the recuperators, there beingindividual valves il for the three exit ports on each wall of the pitfurnaces. 'I'he heat is further controlled by regulation of thepreheated air passing into ports 22 and the combustible gases in ports25 and 26, the gases being controlled by valves $8 and the air throughthe air inlet passages 2|. By separately regulating the fuel and airsupply on each side of the mixing chamber 23, the character of the flameand the heat'of the furnace is positively controlled, and by controllingdampers I8 and el the heat distribution within the furnace may bepositively controlled.

The circulation of the producer gases, the preheated air, thecombustible gases and the products of combustion are illustrated byarrows in Figure 3 ofthe drawings, the single arrow designating thepreheated air; the double arrows, producer gas; triple arrows,combustible gas; and quadruple arrows, the products of combustion.

By the double ring of the pit furnaces, possible regulation of thefurnace temperatures can be maintained, and by directing the heatthrough the center of the furnace in a vertical direction within thecombustion chamber constituted by the walls of the ingots per se, the

latter are subjected-to the most eilcient heating conditions as theheating medium completely envelops the ingots and is at its hottestpoint when entering the furnace which is near the base of the ingots,thus eliminating the overheating of the top of the ingots reducingscaling or oxidation by avoiding direct impingement oi' the flame on thesteel. By thus avoiding direct impingernent of the initial flame on thewalls of the ingots, fusion of the scale with the body of the ingot iseliminated, and upon subsequent rolling of the ingots in the mill, thescale drops 0H. The indirect ilirlng with the initial flame out ofcontact with the ingots. the spacing of the ingots on the furnace hearthto provide combustion spaces Ibetween adjacent ingots to expose amaximum of the ingot walls to the initial heat entering the furnace, andthe cireulation of the products lof combustion over a -niaximum wallarea of the ingots to envelope the ingots in the heating medium, makespossible a lower average .temperature condition throughout the heatingcycle, or in other words produces a minimum Etemperature l.differentiallod between the heating medium and the ultimate ingot temperature. 0naccount of the high preheat available -by the use of the recuperators ofthe construction herein disclosed, gases of low B. t. u. such as blastfurnace gases may be consumed which renders the heating of -ingots bythis fuel a more desirable, eillcient and economical operation.

dampers IBa which may be manipulated vas required through openings 21.The object is to provide means for maintaining a temperaturedifferential between the cold'air to desired be preheated and the wastegas, the quantities of which vary widely for different fuels whenalternated for the same purpose. By means of this by-pass we avoidsetting up undue stresses in the tile in the recuperator 'which wouldcause rupture and require immediate repairs and the |loss of productionfrom the pit. This structure permits the use of blast furnace gas aloneor j in combination with the other richer fuels to obtain higher dametemperatures. without jeopardizing the tile by eliminating excessivetemperature differences by by-passing a portion 'of the surplus Wastegas.

High air preheat temperatures are obtained by utilizing specialrefractory tile construction such as those composed of alumina silicatesin the recuperator. These provide high preheat temperatures, about 300F. above the limit of clay tile and produce higher ame temperatures thanwould otherwise be possible in an ordinary recuperator because thematerial used is non-porous and a better conductor of heat and thereforewhen used in pit furnaces makes possible the substitution of blastfurnace gas in a the recuperator, is used to preheat the gas and le'ndto the combustion of the air and the gas, greater flexibility as toflame temperature range. In Figure 5 these pipes are shown connected tothe burner blocks in the port as they wouldbe arranged in full accordwith the preferred modificatio'n provisions of Figures 17 and 18.

The results to be attained by the improvedpit furnace especially in thedesign of Figures 17 and 18 adapted to either raw hot-producer gas orblast furnace gas, or dual firing of the two in a desired percentage toattain the best flame temperature conditions, are shownby the followinggures which indicate the necessity for the by-passing of a quantity ofthe waste gas. Using producer gas alone as fuel, the ratio of airrequired to waste gas is approximately '1.1 to 12.43; using blastfurnace gas alone, the ratio is about 7.17 to 16.1. i The ratio of fuelvolumes for the two gases is about 6 to 10.4 being raw gas and blastfurnace .gas respectively. It isA evident from the foregoing that thereis a surplus of waste gases from the combustion of blast furnace gaswhen substituted in a furnace for a richer fuel in the same furnaceoperating at like temperatures, performing the same work.

It follows further that the blast furnace gases can-be preheated tovirtually the same temperature as the air, because we nd we have almostequal quantities of waste gas passing through the heat exchanger and the`by-pass recuperator ues thru which we pass the gas in suitable heatresistant alloy pipes, or the equivalent, prior to delivery to theburner ports 26. i

Figures 17 and 18 show the arrangement of the pit-and heat exchangermodification with the b ypass flues lia for waste gas on top of which iscomprises, assembling a plurality of ingots on the hearth of a soakingpit in an upright position, adjacent ingots forming the walls of acombustion space and directing a heating medium at the center of saidspace from the bottom of the pit to the top of the ingots coaxiallytherewith on Heat of combustion+sensiblev heat in fuei+sensible heat inair (Total quantity of .combustion products) x (their mean specificheats) lo Using this formula it is determinable that the actualtemperature of the ame with preheated air at 1600" F. and' cold blastfurnace gas ls 2680 F. However, by using very dense tile in the upperpart of the recuperator designated as h, it is possible to preheat theair to approximately 1900 F. in this practice and the,ame

temperature then becomes 2745 F. This tem' furnace is that of cleaningthe combustible gas passages by the admission of air into the gas mains41 through the air inlets 48 shown in Figure 12 of the drawings. Byadmitting air into the gas to the use of producer gas are burned out ofthe gas ues or passages and this without interrupt# ing the operation ofthe furnaces since one side of thefurnace may be shut down for cleaningwithout interfering with the lfiring of the pit furA naces through theother combustion units.

The following features are made the subject matter of our copendingapplications. SerialNo. 733,812 filed July 5, 1934,-claimscertainfeatures 45 of the furnace temperature controls not claimed in thepresent application; Serial No. 32,534 filed July 22, 1 935. claims afurnace cover and cover lifting and traversing mechanism; and .SerialNo. 47,254 iiled October 29, 1935 claims the relation of the furnaceclosure and furnace sealing means.

We claim:

1. The method of heating steel ingots in a soaking pit furnace whichcomprises; standing the ingots spaced from the vertical walls of thefurnaceto form a combustion chamber of substantial width between theingots, introducing a heating medium from the bottom of the chamber atsubstantially the center thereof, causing said heat to ow in a verticalpath to the top of the cham` ber and subsequently causing the said heatto return in a path substantially parallel to the rst named path to thebottom of the chamber.

2. The method of heating steel ingots which comprises, assembling aplurality of ingots on the hearth of a soaking pit in an uprightposition,

v adjacent ingots forming a wall of a combustion space and directing aheating medium into the furnace chamber on one sideof said ingotscoaxially therewith, and then directing the heating medium to theopposite sides of said ingots in a path substantially parallel tothewall of said ingots to simultaneously uniformly heat all of said ingots.

16 3. The method of heating steel ingots which passages 26 all of thecarbon deposits incidental one side thereof, thence in a downwarddirection on the opposite sides of said ingots to continuously enveloptheir entire surfaces with said heating medium.

4. The method of heating steel ingots which comprisesv assembling aplurality of ingots on the hearth of a soaking pit in spaced relation toexpose their surfaces, directing a heating medium from the center at thebottom to the top of said pit, and causing the heat to diffuse and theprodhearth of a soaking pit in spaced relation to expose their surfaces,directing a heat flame from the center at the bottom to the top of saidpit,

and removing the products of combustion at intervals from the bottom ofthe pit chamber.

6. 'Ihe method of heating steel ingots which comprises assembling aplurality of ingots on the hearth of a soaking pit in spaced relation toexpose their surfaces introducingA gaseous fuel vertically upward intothe pit chamber from the center thereof between the walls of saidingots, and removing the products of combustion ihv a vertical downwardstream from said pit at the bottom thereof.

7. In a pit furnace embodying in combination a heating chamber, arecuperator structure, a fuel mixing chamber, waste gas passages fordirecting the products of combustion from the furnace chamber to therecuperator structure, passages for directing the preheated air to thecombustion chamber, means for burning richer or leaner fuels separatelyor in combination comprising a by-pass for the gas passages around therecuperator structure with regulable means controlling the volume of thegases flowing therethrough, and conduit means adapted to extend throughsaid by-pass for directing the leaner fuel gases to the fuel mixingchamber.

8. In an industrial heating furnace, a furnace chamber, a fuel mixingchamber, a recuperator structure, gas passages opening into said mixingchamber communicating with a source of rich fuel, and gas passagesopening into said mixing chamber leading to a source of 4leaner fuel,waste gas passages for directing the products of cornbustion from thefurnace chamber to the recuperator structure, means for by-passing' aquantity of the products of combustion around the recuperator structure,and regulable means controlling the volume of gases flowing -to theby-pass, the last named gas passages of the mixing chamber havingconduit connections extend ing through the recuperator waste gas by-passto preheat the gases delivered to the -mixing chamber'.-

9..A pit furnace for heating steel ingots, said furnace embodying ahearth, side wall and roof structure for receiving ingots of substantiallength, the ingots resting in spaced relation on their ends upon thehearth of the furnace chamber, said chamber having passages forsupplying combustible fuel mixtures to the furnace chamber at one end ofthe ingots and for withdrawing the products-of combustion at the sameend of the ingots, said passages being in spaced relation to 'obtain adirectional distribution of theproducts of combustion to cause asubstantial portion of the heating medium to pass from the fuel supplysource between the bottom and top of.

l the heating chamber on opposite sides of the m of the products ofcombustion is effected through sinuous paths from the bottom to the top,thence to the bottom of the furnace, and regulating the volume of fuelsupply and the exhaust of the waste gases to thereby regulate thevertical extent of travel of the products of combustion to completelyenvelop the ingots with the heating medium. f

11. The method of heating steel ingots in a closed furnace chamberhaving fuel supply and waste gas outlet ports at one end of the verticalaxis of said chamber, which comprises standing the ingots on end on thefurnace hearth and so placing them relative to the fuel and outlet portsthat the products of combustion entering the furnace chamber aredirected substantially parallel to'and adjacent the walls of the ingots,and regulating the fuel supply and the exhaust of the waste gases tocontrol the distribution of the products of combustion toY completelyenvelop the ingots in the heated environment.

12. The method of heating steel ingots in a soaking pit furnace whichcomprises assembling the ingots on their ends in spaced relation on thefurnace hearth, introducing combustible fuel mixtures into the furnacechamber on one side and at one end of the ingots, directing theproductsof combustion to the opposite end of the ingots with thefiameaxis out of contact with the ingot walls, and withdrawing Vthe productsof combustion at the opposite sides and at the end of initialapplication of heat to said ingots to thereby envelop the sides of theingots. with the heating medium.

13. A pit furnace for heating'steel ingots comprising'a hearth, sidewalls and roof structure vconstituting a heating chamber of sufcientdepth for supporting a plurality of vertically disposed ingots on said'hearth, said chamber having central and peripheral ports at the bottomthereof for the passage of a gaseous heatingv medium to 'generate aplurality of loops of hotl gases extending across and communicating withsaid ports,

the ports being spaced for assembling the vertically disposed ingotstherebetween, said ingots to be enveloped on opposite sides by the loopsof hot gases, and means controlling thefuel supply. and -the exit of theproducts. of combustion ingot walls, directing the products ofcombustion vertically upward parallel .with the longitudinal axis of theingots adjacent one side thereof, then downward to the outlet port atthe bottom of the ingot adjacent the opposite side of the ingot, themajor travel of the products of combustion being in a vertical plane,and controlling the volume of the fuel supply and exhaust gases passingthrough the ports to regulate the length of travel and heat intensity ofthe products of combustion.

15. In a steel ingot heating and soaking pit furnace, `a hearthstructure forsupporting the ingots, a wall and roof structure formingwith the hearth a furnace chamber of substantial depth, fuel supply andwaste gas portsA adjacent one end of thevertical axis of thefurnacechamber, said ports being spaced to divide the chamber into contiguousfiring zones in which the ingots are placed, and regulable meanscontrolling the -fuel supply and exit of the waste gases to extend theproducts of combustion vertically into and from the furnace chamber forenveloping one side of the ingots in travelling from end to end of saidchamber, and to envelop the opposite sides of said ingots in theirreturn travel to the -waste gas outlets of the chamber.

1s. The method of heating sten ingots which comprises, assembling aplurality of ingots on the hearth of a soaking pit in an uprightposition with the walls of the ingots forming a combustion space withthe walls of the soaking pit, directing a heating medium from the bottomof the ingots along one side of said ingots to simultaneously heat allof said ingots and then directingV the low of the heating mediumsimultaneously to all of the opposite sides of said ingots to uniformlyheat the said ingots.

1'7. The method of heating steel, ingots in a soaking pit furnace whichcomprises assembling the ingots on their ends on the furnace hearth,introducing combustible fuel mixtures into the furnace chamber on oneside of the ingots adjacent the bottom thereof, vdirecting the productsof combustion along one side from the bottom to the top ofthe ingots insuch proximity therewith that the mean temperature differential of theheating flame and the ultimate ingot temperature shall be a minimum, andwithdrawing the products of combustion from ports spaced and arrangedadjacent the bottom of the furnace on the opposite sides of the ingotsto envelop the ingots with the heating medium.

18. The method of heating steel ingots in a soaking pit furnace ofsubstantial depth which comprises assembling the ingots on their ends inspaced relation on a furnace hearth with a .wall of the ingots exposedto the fuel inlet of the furnace, and directing a heating mediumvertically inapath parallel to the walls of the ingots andproximatethereto, whereby to maintain a minimum temperature differential of thesembling the ingots on their ends in spaced relation on the furnacehearth and directing a comprises standing the ingots on their ends onthe furnace hearth, directing a heating medium into one end of thefurnace and withdrawing the products of combustion from the same end ofthe furnace on the opposite side of the ingots, the heating medium inpassing into and out of the furnace traversing at least the full length,of one longitudinal side of saidingots.

21. The method of heating steel ingots which comprises standing the ingots on their ends on the furnace hearth, directing a heating mediumfrom the bottom into the furnace and withdrawing the products ofcombustion from the bottom of the furnace on the opposite side of theingots, the heating medium in passing into and out of the furnacetraversing at least the full length of one wall of said ingots.

22. The method of heating ingots which comprises assembling a pluralityof ingots on a furnace hearth with one wall of all of said ingotsexposed to a direct source of ,heat produced by combustion, andexhausting the products of combustion from the furnace to cause them topass along substantially the full length of the walls of said ingotsopposite the wall of direct heat application. 4

23. The method of heating steel ingots which comprises assembling ingotswith their longitudinal axes substantially vertically disposed in asoaking pit furnace with one wail of the ingots exposed to a directsource of heat and the opposite walls of said ingots adjacent a heatreflecting wall of said furnace, and directing the products ofcombustion in one direction of their travel between the ingots and saidheat deflecting wall.

24. The method of heating ingots in'a pit furnace which comprisesstanding the ingots on their endson a hearth to form a combustionchamber between a wall of the furnace and a perforate wall formed by theingots, applying heat continuously at the bottom end of the ingots,flowing the heat unidirectionally from the firing port about the ingotswhile rising vertiing the products of combustion from the bottom of thefurnace. the heating medium in passing into and out of the furnacetraversing at least the full length of one wall of said ingots.

26. The method of heating ingots in a soaking pit furnace having aheating chamber with a port for a gaseous heating medium in a horizontalwall of said chamber, which comprises, assembling the ingots in s pacedrelation on their ends on the hearth of said chamber to form acombustion' space between the ingots, conducting a gaseous heatingmedium continuously from one end of the ingots, between the ingots, in apath substantially parallel to a wall of said ingots and spacedfrom theingots suiiiciently to produce substantially complete reaction of thecombustible mixture before contacting with the ingots to preventexcessive contact of oxidizing gases with the walls of the ingots, andcausing the heating medium to travel in a substantially vertical pathextending to said port to thereby .traverse at least the full length ofone wall of said ingots.

" v" rail A. MORTON.

HOWARD F. SPENCER.

